A tapered aeration activated sludge plant is to be designed for a population of 85,000 persons. Pertinent data are: influent flow = 95 gal/cap-day (360 ℓ/cap-d), influent bod5 = 210 mg/ℓ, primary clarification removes 33% of the influent bod5, effluent bod5 = 10 mg/ℓ, mlss = 2500 mg/ℓ, mlvss = 75% of the mlss, sludge density index = 10,000 mg/ℓ, reaction time = 5.0 hr based on Q + R, Y = 0.60 mg mlvss/mg bod5 removed, and ke = 0.06 day−1. Determine, using USCS units:a. The reactor basin volume.b. The waste activated sludge production per day.c. The waste activated sludge flow, in gallons per day, if the sludge is wasted from the recycle line and the specific gravity of the wet sludge is 1.01.d. The mean cell residence time. θe, for the reactor basin.
